The Psychic Immune System theorizes the existence of a hidden variable that acts via both unconscious and conscious processes to protect humans individually and collectively from mortal threats. Much like the physical immune system, the psychic immune system scans for danger, protects, heals, and ensures human safety and survival. Kroth argues that it isn't just luck that has enabled people to survive the multitude of epidemics, wars, and environmental disasters that could have resulted in extinction, but rather the work of a complex system that has enabled us to survive. Scrutinizing a variety of past and present threats, Kroth points to traces of a systematic force that has protected humans. Recommended for scholars of psychology, history, and political science.